In recent years, with the spread of PET bottle drinks, beverage manufacturers have been selling a large variety of products. Such PET bottle products are decorated with design-focused labels for the purpose of clearly differentiating them from other brands, improving their image to customers, etc.
As PET bottle labels, those having a substrate of a polyester-based shrink film, polystyrene-based shrink film, or polyolefin-based shrink film are known. Among these, polystyrene-based shrink films are generally used for their ease of cutting along a perforated line, shrinking quality, etc.
A number of suggestions has been made regarding such polystyrene-based shrink films. For example, to provide a shrink film having excellent low-temperature shrinkability, natural shrinkability (shrinkability under ordinary temperature), etc., a three-layer heat-shrinkable laminate film having outer layers and an intermediate layer of a styrene-butadiene block copolymer has been suggested (see, e.g., Patent document 1). Further, for the purpose of improving blocking resistance, natural shrinkage resistance (resistance to shrinkage under ordinary temperature), and the like under long-term storage, shrink films containing, as essential ingredients, rubber modified styrene, a lubricant, and inorganic or organic fine particles have been suggested. (See, e.g., Patent document 2.) However, no film has yet been obtained that could solve the problem of ink skipping during the printing process, in addition to having a smooth film surface and blocking resistance.
Patent document 1: Japanese Unexamined Patent Publication No. 2004-74687
Patent document 2: Japanese Unexamined Patent Publication No. 2002-161147